Nine women have been ordained as Roman Catholic priests in a secret ceremony in Austria on Saturday which could lead to their excommunication from the church.
The women, who are from Austria, Germany and the United States, gathered on a boat on the River Danube for the ordination.
The ceremony was conducted by Argentine Archbishop Romulo Braschi, who was himself ordained as a Roman Catholic priest but has since joined a church not recognised by the Vatican.
The ordination of the women is fiercely opposed by leaders of the Catholic Church in Austria and Germany, who described it as a "cult spectacle".
The group, who include several pioneer theologians, argue that the Church's refusal to ordain women has no basis in the scriptures.
But Roman Catholic groups campaigning for the ordination of women distanced themselves from the group, saying it was better to fight within the church.
Austrian church authorities said that the ceremony represented "a fundamental break with the Roman Catholic Church".
"Only men can be ordained," said Maximillian Aichern, the bishop of Linz.
"The simulated ordination of a woman is not only invalid, but also blatantly contradicts the rules of the Church."
The Bishop of St Poelten, Kurt Krenn, warned that they could be excommunicated.
But BBC religious affairs correspondent Robert Pigott says that despite such warnings the Vatican may well decide that the best way of neutralising what is, effectively, a high profile protest, is to ignore the women and their future ministry.
'Sign of protest'
The Church's arguments have been dismissed as groundless by those taking part.
"The Vatican is used to treating as sects anyone who differs with its dogma," Archbishop Braschi, now a member of the Jesus Rey Church, said.
"Both the doctrine of the ban on women priests and the law that is based on it reflect a heresy," wrote theologians Ida Raming and Iris Mueller - two of the women being ordained.
"The women who will take part in the 'illicit' ordination understand their action as a clear sign of protest - a protest against doctrine and Church law which discriminates against women."
They describe their defiance as an act of prophecy that could herald a fundamental leap within the Church.
The Catholic Church has always refused to ordain women because Jesus Christ selected only men as his apostles.
Supporters of women priests argue that this condemns women to a second class status in perpetuity - and makes the Church look increasingly out of touch with the lives of many of its followers.